Semi-fluid lubricant



SEMLFLUID LUBRICANT Paul R. McCarthy, Allison Park, Pa., assiguor to Gulf Research & Development: Company, Pittsburgh, Pa., a corporation of Delaware No Drawing, Appli'cationMay 29,1956, SerialNo. 587,966

Claims; (Cl. 252-57) This invention relates toan improved semi-fluid: lubricant and more particularly to a thixotropic lubricating;

composition having high adhesive properties in the liquid: state.

In certain types of lubrication there are encountered conditions under which neither greasesnor-liquid: oils are entirely satisfactory lubricants. For example, in the lubrication of certain textile machinery such as plain bearings onlooms, top rolls, roll necks andsaddles of drawing, roving and spinning frames, it is desirable that the lubricant be of such consistency, that it will remain between the working surfaces and not be lost by dripping, leakage or centrifugal force. At the same time, his: desirable that the lubricant be of relatively low viscosity under operating conditions so as to neither; impede the-operation of the mechanism nor increase the power consumption.

Employing a textile-machinery. lubricantwhichwill stay on the bearing surface is important not only: from. the standpoint of the life of the hearing, but also from the standpoint of the product of the mill. Obviously, lubrication failure of the bearing will result in costlyshuedown of the machinery. Also, leakage of. lubricant onto the productof the mill, whether thread. or Woven fabric, will result in undesirable staining-of the fabric;

In addition tothe above requirements the, textile machinery lubricant must feedthrough. wickswithout: clogging and must be dispensable from ordinary squirt-type oil cans. While liquid oils can be dispensed from oilcans and aregenerally satisfactory'lubricants, as a general rule they do not have good metal adhesion properties. Greases. have good metal adhesion, properties but are undesirable in that they can notbeappliediby-wick feed or by ordinary oil cans.

Semi-fluid oils of the soap-thickened.typehavexbeen extensively used for lubricating textile machinery. Soapthickened lubricants, however, have certain; shortcomings in that frequently lumps of soapappear which clog the.

wicks. The. soap-thickened lubricants: have also. been undesirable in that lubricants having identical properties1 are difiicult to reproduce. Furthcrmmi Soap-thickened lubricants having suitable adhesive properties, as;a;general: rule, have some unsatisfactory property such, as. being stringy.

It is, therefore, an object achieved by this invention to provide an easily reproducible lubricating. composition whichwill be sufficiently fluid to apply from anordinary squirt-type oil can and will remainfluid while the bearings on which it is placed are in operationbutwill form a light gel when the bearings are. not inoperation.

This and other objectsachieved by this inventionwill become apparent from the following detailed discussion.

I have discovered that a semi-fluid oil having thixotropic.

characteristics and improved metaladhesion. inthe'liquid state can be preparedfrom a high viscosity hydrocarbon. oilbyv compounding therewith smallamountsof each of polymerized ethylene and a hydrogenated rosin, The

1 ited States Patent 2,816,869 Patented Dec. 17, 1957 semi-fluid composition of the invention, since it does not rely. upon soap as a gelling agent, is to be distinguished from greases. insofar as the mode of obtaining a gel consistency is concerned.

The hydrocarbonv oil employed in the preparation of the thixotropic composition according to this invention can be. either a refined or semi-refined parafiinic-, naph-- thenic-,. or asphalt-base oil, or the oil can be a synthetic oil having a viscosity above about 400 SUS at 100 F. and preferably having a viscosity. of about 400 to. 4000-SUS at 100 F. If desired, ablend of oils of suitable viscosity can be employed instead of a single .oil, by means of which any desiredviscosity within the range of 400to 4000. .SUS. at- 100 F. canbe secured; The. amount: of oil employed constitutes from about r0 99 percent by weight of the. total composition. Naturally, the optimum amount: of oil employed in any given instance will. depend, upon the particular oil. employed as well as upon. the characteristics desired in the final composition.

The polymerized ethylene is a polymerization product of ethylene having a molecularyweight of about 1000 to 40,000 or. more. Polyethylenes'havinga molecular weight within this range, i. e., 19,000, are characterized by. the following approximate characteristics:

Softening point, "C 108 Tensile strength, p. s. i 1200 Yield point, p. s. i 1450 These polymerized ethylene compounds are obtained.

by the'thermal or catalytic polymerization of ethylene at high pressure. not a part of the present invention. Theamount of polymerized ethylene employed constitutes about 0.2 to about. 5 percent by weight of the total. composition.

The hydrogenated rosin employed according to the invention is a rosin of at least about 40 percent saturation to and including fully hydrogenated rosin. Rosin, sometimes called colophony, is the residue obtained on distilling turpentine from hard pine resin. Abietic acid, C H O is the chief constituent of rosin and is obtained from. the latter by distillation. Abietic acid is a carboxylic acid containing two double bonds. Hydrogenated rosin is obtained by the addition of hydrogen to the double bonds of abietic acid. The amount of hydrogen added may, be sufficient to saturate the two unsaturated. bonds of abietic acid or it may be any amount to produce substantial partial hydrogenation. A particularly useful hydrogenated rosin for the purposes of my, invention is one which has been hydrogenated to about 50 to about 60 percent of capacity and has a melting point of about 168 F. The quantity of the hydrogenated rosin employed constitutes from about 0.2 to about 5 percent by weight of the total composition. In general, improved, metal adhesion characteristics are obtained when the weight ratio of the hydrogenated rosinto the polymerizedethylene is between. about 1:3 and about 3:1. In any event the mixtureof. hydrogenated rosin and polymerized ethylene is added in an amount sufficient to increase the viscosity of the hydrocarbon, oil and to impart thixotropic characteristics thereto.

In preparing the improved lubricant of my invention I can. also incorporate in the lubricant one or more. of. the so-called addition agents normally added to lubricating. oils for a specific purpose including an anti-oxidant, a corrosion inhibitor, an anti-rust agent, an extreme pressure agent, an anti-foam agent and an oiliness agent. Corrosion. inhibitors are particularly desirable in: com: positions used in corrodible alloy, bearings. Among. the corrosion inhibitors suitable for. the purpose of the invention are dibenzyl disulfide, alkyl phenyl sulfides,

The method of forming the polymers is alkyl phosphites, alkaryl phosphites and sulfurized terpenes. In instances where the lubricant is subjected to prolonged use under oxidizing conditions, I advantageously incorporate in the lubricant a small amount of an oxidation inhibitor such as an alkali insoluble phenol, i. e., 2,6-di-tertiary-butyl-4-methylphenol; 2,4,6-tri-tertiary-butylphenol; etc., and/or a small amount of a diaryl amine. As examples of some of the diaryl amines which can be used in the composition of the invention may be mentioned diphenylamine, phenyl alpha naphthylamine, phenyl beta naphthylamine, alpha alpha-, alpha beta-, and beta beta-, dinaphth lamines, and the like. The amount of the conventional additive agents employed will depend to a large extent upon the conditions to which the composition is subjected, as well as upon the particular additive used. For instance, when the composition is subjected to prolonged use under oxidizing conditions, such as under extreme pressure and temperature, the oxidation inhibitor and extreme pressure agent requirements will be much greater than when relatively mild operating conditions are encountered. Generally, the amount of the anti-oxidant employed is between about 0.1 and 1.5 percent by weight based upon the weight of the total composition. In any event, the amount of additive employed is sufficient to accomplish the purpose for which it is intended without deleteriously affecting the other desirable characteristics of the composition.

In compounding the semi-fiuid lubricant of the invention, various compounding and blending procedures can be used. In accordance with one embodiment, the hydrogenated rosin is placed in a vessel and then heated until it is liquid. The temperature thus attained is about 200 F. The polymerized ethylene is then added with stirring to the melted hydrogenated rosin while continuing to heat to 450 F. The mixture is then held at 450 F. for a time sufficient to effect a uniform dispersion. The time required depends upon the size of the batch as well as the efficiency of the dispersing means. An oil concentrate of the hydrogenated rosin-polymerized ethylene dispersion is then prepared by adding an amount of oil equivalent to the combined weight of the hydrogenated rosin and polymerized ethylene. Heating at 450 F. with stirring is continued until a uniform concentrate is obtained. The concentrate is then added to the base oil having the desired viscosity at 240 F. Stirring is continued to obtain a uniform blend. The mixture is then cooled to room temperature with or without stirring depending upon the viscosity desired in the final product. I have found that cooling Without stirring from 240 F. to room temperature results in a product having a higher viscosity than a similar product which has been cooled from 240 F. to 120 F. with stirring. If a conventional additive such as an anti-oxidant is employed, it can be added to the dispersion of polymerized ethylene and hydrogenated rosin, or it can be added to the oil prior to the preparation of the concentrate. Of course, other compounding means can be employed without deviating from the scope of the invention.

The advantageous properties obtained by incorporating hydrogenated rosin and polymerized ethylene in a 750/45 Texas mineral oil as compared with the oil itself will be illustrated in connection with a metal adhesion test which is indicative of the adhesion characteristics obtainable in commercial application of a lubricant.

The metal adhesion test employed in comparing the lubricating compositions is that test ordinarily employed in determining the adhering characteristics of a grease. In conducting the test, a polished brass or steel disc with a concave surface is mounted on a vertical motor shaft so that the plane of the disc is in a horizontal position. The disc is tared. One tenth gram of lubricant is placed on the disc. The disc plus the lubricant is then reweighed. The disc is then attached to. the motor shaft. The entire disc is encased in a closed chamber the temperature of which is thermostatically controlled. The motor is then run for a period of seven minutes at a selected speed of 200 to 1000 R. P. M. at a selected temperature of to 200 F. At the end of the seven-minute period, the disc plus lubricant is reweighed and the lubricant remaining on the disc is calculated as percent lubricant retention.

In preparing the following compositions, a lubricating oil having a viscosity of about 750 SUS at 100 F. was prepared by mixing 68 parts by volume of a Texas oil having a viscosity of about 500 SUS at 100 F. with 32 parts by volume of a Texas oil having a viscosity of about 1900 SUS at 100 F. Various amounts of polymerized ethylene and hydrogenated rosin were employed as shown. The polymerized ethylene was a solid having a molecular weight of about 19,000. The hydrogenated rosin employed was a solid having a melting point of about 168 F. The double bonds of the rosin acids had been saturated to an extent of about 50 to 60 percent. The blending procedure employed in preparing the compositions was in accordance with the embodiment described hereinabove. In preparing these compositions the rate of cooling from 240 to 120 F. was increased by stirring. Cooling from 120 F. to room temperature was without stirring.

Table 1 A B 0 D Composition. percent by wt.:

750/4.5 Texas oil 98 98. 5 99 Hydrogenated rosin 1.332 1.0 0. 666 Polymerized ethylene 0. 668 0.5 0. 334 Ratio of Hydrogenated rosin to Polymerized ethylene 2:1 2:1 2:1. Inspection:

Viscosity, SUS- at 100 F 753 1, 597 1, 228 1, 153 at 210 F 62 80 4 74. 4 70.3 Adhesion to metal, percent retained (0.1 gm. of lubricant applied to disc rotated for 7 minutes at room temperature)- at 200 R. P. M 100 100 100 100 at 400 R. P. M. 50 100 90 at 600 R. P M 40 80 7O 60 at 800 R. P. M- 30 60 45 35 at1000 R. P. M 40 Adhesion to metal, percent retained (400 R. P. M.)-

at 80 F 63 98 97 85 65 100 45 93 93 88 It can be seen from the data in the above table that compositions B, C and D containing from 1 to 2 percent by weight of a mixture of hydrogenated rosin and polymerized ethylene in a 2 to 1, respectively, weight ratio gave remarkably improved metal adhesion characteristics. In the first series of tests, the temperature was maintained constant while varying the speed between 200 and 1000 R. P. M. In the second series of tests, the speed was maintained constant while varying the temperature between 80 and F. In each series of tests, the compositions of the invention were strikingly superior.

The results of additional tests employing a composition containing two percent by weight of a mixture of hydrogenated rosin and polymerized ethylene in ratios between 1:3 and 3:1 are shown in Table 2. These compositions were prepared by the same procedure used in preparing the compositions reported in Table 1.

The data in Table 2 again show the improved metal adhesion characteristics of compositions within the scope of the invention. It will be noted that compositions B, C and E .wherein the ratio of hydrogenated rosin to polymerized ethylene is 1:3, 1:2 and 2:1, respectively, gave particularly good retention of the lubricant at temperatures of 80 to 160 F.

As disclosed hereinabove, I have found that cooling without stirring from 240 F. to room temperature results in a producthaving a higher viscosity. This point Table 2 A B C D E F Composition, percent by wt.:

750/45 Texas oil 100 98 98 98 98 98 Hydrogenated rosin 0. 48 0.66 1. 1. 34 1. 52 Polymerized ethylene 1. 52 1. 34 1.0 0.66 0. 48 Ratio of Hydrogenated rosin to Polymerized ethylene 1:3 1:2 1 1 2:1 3:1 Inspection:

Viscosity, SUS- at 100 F 753 2, 630 2, 340 1, 118 1, 597 1, 326 at 210 F 62 8 86. 80.2 80. 4 70. 5 Adhesion to metal, percent retained (400 R. P. M.)-

can be illustrated by inspecting the viscosities of lubricating compositions which contain the same proportions of hydrogenated rosin and polymerized ethylene, the only difference being the manner in which cooling is effected. In Table 3, the compositions were prepared according to the blending procedure described hereinabove. After uniform blends were obtained, compositions A and C were cooled from 240 F. to room temperature without stirring; compositions B and D were cooled from 240 to 120 F. with stirring and then to room temperature without stirring.

The above data show that cooling without stirring gives products having higher viscosities than products obtained with increased cooling by stirring. It is also to be noted that compositions having a ratio of hydrogenated rosin to polymerized ethylene of 2 to 1 are superior in their metal adhesion characteristics to compositions having a ratio of 1 to 1.

While the above compositions were prepared using a 68-32 blend of 500/3 and 1900/5 Texas oils, equally satisfactory compositions can be obtained by varying the ratio of oils and by using oils of different viscosities. Typical properties of such compositions are as follows:

Composition, percent by wt.:

100/2 Texas oil 43 20 1900/5 Texas oil-.- 55 78 Hydrogenated rosin 1.332 Polymerized ethylene 0.668 Ratio of hydrogenated rosin to polymerized ethylene 2:1 2: 1 Inspection:

Gravity, API 22. 0 21.1 Viscosity, SUS- at 100 F 728 1, 535

at 210 IL--- 69.0 94.5 Viscosity Index- 74 64 Flash point, 0. 0.: 355 385 Fire point, 0. 0.: 405 445 Pour point, F 5 Color, ASTM Union 4. 75 5. 5 Neutralization Value, ASTM D 97453T Total Acid N o.-- 2.1 2. 1 Ash, percent 0.012

While my invention has been described with reference to various specific examples and'embodiments, it will be understood that the invention is not limited to such examples and embodiments and may be variously practiced within the scope of the claims hereinafter made.

I claim:

1. A lubricating composition consisting essentially of a major proportion of a hydrocarbon oil having a viscosity above about 400 SUS at 100 F. and a minor proportion, sufficient to increase the viscosity of the oil and to impart thixotropic characteristics thereto, of a mixture of hydrogenated rosin of at least about 40 percent saturation and polymerized ethylene having a molecular weight between about 1000 and about 40,000, the weight ratio of hydrogenated rosin to polymerized ethylene being between about 1:3 and about 3:1.

2. A thixotropic lubricating composition consisting essentially of a major proportion of a hydrocarbon oil having a viscosity of about 400 to about 4000 SUS at 100 F., about 0.2 to about 5 percent by weight of polymerized ethylene having a molecular weight between about 1000 and about 40,000, and a hydrogenated rosin of at least about 40 percent saturation, the weight ratio of hydrogenated rosin to polymerized ethylene being between about 1:3 and about 3:1.

3. A thixotropic lubricating composition consisting essentially of a major proportion of a hydrocarbon oil having a viscosity of about 400 to about 4000 SUS at 100 F., about 0.2 to about 5 percent by weight of polymerized ethylene having a molecular weight between about 1000 and about 40,000, and about 0.2 to about 5 percent by weight of a hydrogenated rosin of at least about 40 percent saturation.

4. A thixotropic lubricating composition consisting essentially of a major proportion of a hydrocarbon oil having a viscosity of about 400 to about 4000 SUS at 100 F., about 0.2 to about 5 percent by weight of polymerized ethylene having a molecular weight between about 1000 and about 40,000, and about 0.2 to about 5 percent by weight of a hydrogenated rosin of at least about 40 percent saturation, the weight ratio of hydrogenated rosin to polymerized ethylene being between about 1:3 and about 3:1.

5. A thixotropic lubricating composition consisting essentially of a uniform mixture of about to about 99 percent by weight of a mineral lubricating oil having a viscosity of about 400 to about 4000 SUS at 100 F., about 0.2 to about 5 percent by weight of polymerized ethylene having a molecular weight of about 19,000, and about 0.2 to about 5 percent by weight of a hydrogenated rosin saturated to an extent of about 50 to about 60 percent, the weight ratio of hydrogenated rosin to polymerized ethylene being between about 1:3 and about 3:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,221,953 Read Nov. 19, 1940 2,270,319 Lieber Jan. 20, 1942 2,627,938 Frohmader Feb. 10, 1953 2,628,187 Frohmader Feb. 10, 1953 2,691,647 Field Oct. 12, 1954 2,762,775 Foehr Sept. 11, 1956 

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF A HYDROCARBON OIL HAVING A VISCOSITY ABOVE ABOUT 400 SUS AT 100*F. AND A MINOR PROPORTION SUFFICIENT TO INCREASE THE VISCOSITY OF THE OIL AND TO IMPART THIXOTROPIC CHARACTERISTICS THERETO, OF A MIXTURE OF HYDROGENATED ROSIN OF AT LEAST ABOUT 40 PERCENT SATURATION AND POLYMERIZED ETHYLENE HAVING A MOLECULAR WEIGHT BETWEEN ABOUT 1000 AND ABOUT 40,000 THE WEIGHT RATIO OF HYDROGENATED RESIN TO POLYMERIZED ETHYLENE BEING BETWEEN ABOUT 1:3 AND ABOUT 3:1. 